Piperine inhibits proliferation of human osteosarcoma cells via G2/M phase arrest and metastasis by suppressing MMP-2/-9 expression.

The piperidine alkaloid piperine, a major ingredient in black pepper, inhibits the growth and metastasis of cancer cells both in vivo and in vitro, although its mechanism of action is unclear. Furthermore, its anticancer activity against osteosarcoma cells has not been reported. In this study, we show that piperine inhibited the growth of HOS and U2OS cells in dose- and time-dependent manners but had a weaker effect on the growth of normal hFOB cells. Piperine inhibited osteosarcoma cell proliferation by causing G2/M phase cell cycle arrest associated with decreased expression of cyclin B1 and increased phosphorylation of Cyclin-dependent kinase-1(CDK1) and checkpoint kinase 2 (Chk2). In addition, piperine treatment inhibited phosphorylation of Akt and activated phosphorylation of c-Jun N-terminal kinase (c-JNK) and p38 mitogen-activated protein kinase (MAPK) in HOS and U2OS cells. Piperine induced colony formation in these two cell types. We proved that piperine could suppress the metastasis of osteosarcoma cells using scratch migration assays and Transwell chamber tests. Moreover, gelatin zymography showed that piperine inhibited the activity of matrix metalloproteinase (MMP)-2/-9 and increased the expression of tissue inhibitor of metalloproteinase (TIMP)-1/-2. Taken together, our results indicate that piperine inhibits proliferation, by inducing G2/M cell cycle arrest, and the migration and invasion of HOS and U2OS cells, via increased expression of TIMP-1/-2 and down-regulation of MMP-2/-9. These findings support further study of piperine as a promising therapeutic agent in the treatment of osteosarcoma.